JPWO2011055765A1 - Non-consumable electrode arc welding equipment - Google Patents

Abstract

Provided is a non-consumable electrode type arc welding apparatus that does not generate high-frequency noise at the time of arc start, can prevent a start failure, and can reduce wear of the electrode tip. A voltage is applied between the electrode part and the nozzle 1b, the torch 1 provided with the electrode part and the nozzle 1b, gas supply means 8 and 9 for supplying the shield gas flowing through the gap between the electrode part and the nozzle 1b to the torch 1, and the nozzle part 1b. A first power supply 7 for generating a pilot arc 14 when applied, a second power supply 6 for generating a main arc by applying a voltage between the electrode and the workpiece, and a controller for controlling the first power supply 7 and the second power supply 6 In the non-consumable electrode type arc welding apparatus provided with 5, the electrode portion includes an electrode 1 a and an electrode gripping portion 13 for gripping the base portion of the electrode, and the electrode gripping portion 13 is directed toward the nozzle 1 b on the nozzle 1 b side. A protruding protrusion 13a is provided, and the protrusion 13a and the nozzle 1b are brought into contact with and separated from each other.

Description

  The present invention relates to a non-consumable electrode type arc welding apparatus for joining metals, and more particularly to a non-consumable electrode type arc welding apparatus for performing welding by generating a main arc after generating a pilot arc.

<Conventional technology to generate pilot arc>
In TIG (Tungsten Inert Gas) arc welding and plasma arc welding using non-consumable tungsten as an electrode, a high-frequency voltage of several thousand volts is superimposed and applied between the electrode tip of the welding torch and the welding base material (workpiece). Is generally generated. At the time of such arc generation, a method of generating a main arc for welding after generating a pilot arc corresponding to a seed fire in a torch in advance has been used. For example, Patent Document 1 discloses that when a pilot arc is generated, the pilot arc generating gas is temporarily increased to obtain a good pilot arc and then the main arc is transferred.
Patent Document 2 discloses that the nozzle and the electrode that are in contact with each other are separated by the pressure of the plasma gas, and the contact spark generated at that time is transferred to the arc for processing.

Japanese Unexamined Patent Publication No. 63-194867 Japanese Unexamined Patent Publication No. 3-106572

<Problem of Patent Document 1>
However, in the method of Patent Document 1, when generating a pilot arc, a high-frequency power source is used in addition to the direct-current power source for the pilot arc, and high-frequency noise generated from the high-frequency power source adversely affects peripheral electronic devices. There was a problem of fear.
In addition, an oxide insulating film is formed on the electrode surface and the nozzle inner surface in association with the pilot arc generated between the electrode and the nozzle. Since this oxide film is deposited by repeating the arc start, there is a problem that if the oxide film is not periodically removed or parts are not replaced, the pilot arc is difficult to occur and the arc start fails.
<Advantages of Patent Document 2>
On the other hand, the method of Patent Document 2 does not use a high-voltage and high-frequency power source when a pilot arc is generated, so that the problem of noise does not occur.
Further, at the time of arc start, the electrode and the nozzle (or the electrode and the auxiliary electrode) are repeatedly contacted and separated.
This contact operation is advantageous for removing the oxide film, and the oxide film is less likely to be deposited than in Patent Document 1.
<Problem of Patent Document 2>
However, this action is due to the spring being compressed by the shielding gas. Since the force that presses the electrode against the nozzle by the spring (or the force that presses the auxiliary electrode against the electrode) is weak, the oxide film cannot be removed sufficiently by the contact between the two, solving the problem that the arc start characteristics gradually deteriorate Not done.
In addition, there is a problem in that the tip of the electrode is damaged or consumed by bringing the tip of the electrode into contact with the nozzle.
<Object of the present invention>
The present invention has been made in view of the above problems, and the object thereof is to prevent generation of high-frequency noise at the time of arc start in non-consumable electrode type arc welding, further to prevent arc start failure, and to reduce wear of the electrode tip. An object of the present invention is to provide a non-consumable electrode type arc welding apparatus.

In order to solve the above problem, the present invention is configured as follows.
The first invention relates to a non-consumable electrode type arc welding apparatus, comprising a torch comprising an electrode part and a nozzle arranged on the outer periphery of the electrode part with a gap between the electrode part and the electrode part and the nozzle. A gas supply means for supplying a shielding gas flowing through the gap to the torch, a first power source for generating a pilot arc by applying a voltage between the electrode portion and the nozzle, and the electrode and the workpiece In the non-consumable electrode type arc welding apparatus, comprising: a second power source for generating a main arc by applying a voltage therebetween; and a control unit for controlling the first power source and the second power source. An electrode and an electrode gripping part for gripping a base part of the electrode, the electrode gripping part having a protrusion projecting toward the nozzle on the nozzle side, and the torch is configured to extend the electrode part within the torch. axis Moved is characterized by having a moving mechanism for contacting and separating the said nozzle and the protrusion direction.
According to a second invention, in the first invention, when the projection and the nozzle are brought into contact with each other by the moving mechanism, a shield gas is circulated through the gap between the electrode gripping portion and the nozzle secured by the projection. It is characterized by that.
According to a third invention, in the first invention, the pilot arc is generated by the first power source between the protrusion and the nozzle by bringing the protrusion and the nozzle into contact with each other and separating them from each other by the moving mechanism. It is characterized by that.
According to a fourth invention, in the third invention, the pilot arc is moved to the tip of the electrode by the shield gas, and the pilot arc is transferred to a main arc between the electrode and the workpiece by the second power source. It is characterized by letting.
A fifth invention is characterized in that, in the first invention, the moving mechanism is an air cylinder.
A sixth invention is characterized in that, in the first invention, the electrode gripping portion and the nozzle are made of a copper alloy.
A seventh invention is the first invention, comprising: an articulated robot having the torch attached to a tip; and a robot control device that controls the robot, wherein the robot control device serves as the control unit, the first power supply and the The second power source is controlled.
The eighth invention is characterized in that, in the first invention, the tip of the electrode is exposed from the tip of the nozzle and TIG arc welding is performed.
A ninth invention is characterized in that, in the first invention, the whole electrode is covered by the nozzle and plasma arc welding is performed.

According to the present invention, a touch start type pilot arc generation point is provided inside the torch, first the pilot arc is generated by the pilot power source inside the torch, and immediately thereafter, the pilot arc is moved to the tip of the non-consumable electrode by the gas. Let The pilot arc that has moved to the tip of the electrode is maintained by a pilot power source.
At the start of arc welding, a pilot arc that has moved to the tip of the electrode is used as a spark, and an arc is generated between the tip of the electrode and the workpiece by the main power source.
According to the non-consumable electrode type arc welding apparatus of the present invention, no high-frequency noise is generated because a high-frequency power source is not used when a pilot arc is generated, and the projection and nozzle of the electrode gripping part that are pilot arc generation points inside the torch Since the oxide film generated by the pilot arc generation is removed by contacting a part of the pilot arc with a strong force, the start error of the next pilot arc can be prevented and a good arc start can be realized. .
In addition, since the electrode tip and nozzle are not in contact with each other even when a pilot arc occurs, it is possible to reduce the wear on the electrode tip and prevent the oxide film from adhering to the electrode tip. Can contribute.

FIG. 1 is a diagram showing an overall configuration of a non-consumable electrode type arc welding apparatus. FIG. 2 is a side view of the torch. FIG. 3 is a top view of the torch. FIG. 4 is a schematic view of a side cross section of a tip portion of a torch for TIG welding. FIG. 5 is a perspective view of the electrode portion. FIG. 6 is a front view of the electrode portion. FIG. 7 is a timing chart showing the vertical movement of the electrode part, the flow rates of the center gas and the shield gas, the current by the pilot power supply, and the change of the current by the main power supply. FIG. 8 is a schematic diagram of a side cross section of the tip portion of the TIG welding torch at t1 in FIG. FIG. 9 is a schematic diagram of a side cross section of the tip portion of the torch for TIG welding at t2 in FIG. FIG. 10 is a schematic side sectional view showing a state where the pilot arc has moved to the nozzle tip. FIG. 11 is a schematic diagram of a side cross section of the tip portion of the torch for TIG welding at t3 in FIG. FIG. 12 is a schematic diagram of a side cross section of the tip portion of the TIG welding torch at t5 in FIG. FIG. 13 is a schematic view of a side cross-section of the plasma welding torch tip. FIG. 14 is a schematic diagram of a side cross section of the plasma welding torch tip at t1 in FIG. FIG. 15 is a schematic diagram of a side cross section of the plasma welding torch tip at t2 in FIG. FIG. 16 is a schematic side sectional view showing a state where the pilot arc has moved to the nozzle tip. FIG. 17 is a schematic diagram of a side cross section of the plasma welding torch tip at t3 in FIG. 18 is a schematic diagram of a side cross-section of the plasma welding torch tip at t5 in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Overall configuration of non-consumable electrode arc welding equipment>
FIG. 1 is a diagram showing an overall configuration of a non-consumable electrode type arc welding apparatus.
In this embodiment, a TIG welding apparatus will be described as an example.
1 is a torch and 2 is a workpiece to be welded. The torch 1 is attached to the tip of the robot 3 via an attachment jig 4. The robot 3 is a multi-joint robot having a plurality of joints, and the position and posture of the torch 1 relative to the workpiece 2 can be freely changed by appropriately controlling the operation of each joint. The robot 3 is controlled by the controller 5.
6 is a main power source for supplying welding power between the torch 1 and the work 2, and 7 is a pilot power source for generating a pilot arc by supplying power between the electrode in the torch 1 and the nozzle at the tip of the torch 1. It is. Reference numerals 8 and 9 denote gas cylinders for supplying an inert gas such as argon as a shielding gas into the torch 1. Although details will be described later, in this embodiment, two gas cylinders are provided because the shield gas is duplicated.

<Up and down movement of torch 1>
Reference numeral 10 denotes an air compressor that supplies air for moving the electrodes in the torch 1 up and down. The configuration inside the torch 1 will be described later.
11 is an optical sensor for detecting the presence or absence of the occurrence of arc by the light emitted by the arc. Although omitted in FIG. 1, a cooling water circulation device that circulates cooling water in the torch 1 and cools the electrodes is also provided.
In FIG. 1, the torch 1 is attached to the tip of the articulated robot and moved, but this is only an example of the welding apparatus of the present invention, and the torch 1 may be moved by means other than the articulated robot. Good.

<Function of controller 5>
In addition to the robot 3, the controller 5 controls the entire welding apparatus such as ON / OFF of power supply to the torch 1 by the main power supply 6 and the pilot power supply 7 and control of the flow rate of gas supplied from the gas cylinders 8 and 9 to the torch 1. It has a function to supervise.

<Description of the side of the torch 1>
FIG. 2 is a side view of the torch 1, and FIG. 3 is a top view of the torch 1 viewed from the direction of the white arrow in FIG. 2 and 3, the same parts are denoted by the same reference numerals.
1a is a tungsten electrode, and 1b is a nozzle. The nozzle 1b is made of a copper alloy. Reference numerals 1c and 1d denote air supply ports which are connected to the air compressor 10 and supply compressed air from the air compressor 10 into the torch 1. This compressed air is used for the vertical movement of the electrode in the torch 1.
Reference numerals 1f and 1h denote shield gas supply ports supplied from gas cylinders 8 and 9, respectively, and supply shield gas into the torch 1. The shield gas passes through the torch 1 and is discharged from the tip of the torch 1.
Reference numerals 1e and 1g denote a discharge port and a supply port for cooling water to be circulated in the torch 1, respectively.

<Description of the tip of the torch 1>
FIG. 4 is a schematic view of a side cross section of the tip portion of the torch 1.
The tungsten electrode 1a is gripped by an electrode gripping portion 13 at the tip of the electrode support member 12, and the electrode gripping portion 13 is made of a copper alloy like the nozzle 1b.
In the state of FIG. 4, a space is provided between the tungsten electrode 1 a and the electrode gripping portion 13 and the nozzle 1 b, and in this space, a shield gas (indicated by reference numeral G <b> 1) supplied from one of the two gas cylinders. The black arrow) flows from the top to the bottom of the figure. Hereinafter, this shielding gas is referred to as center gas.
A voltage is applied by a pilot power source 7 between the electrode gripping portion 13 that grips the tungsten electrode 1 a and the nozzle 1 b that is provided so as to surround the electrode gripping portion 13.

<Center gas G1 and shield gas G2>
A space is further provided between the outer periphery of the nozzle 1b and the outer wall of the torch, and is different from the gas cylinder that supplies the center gas G1, and the shield gas supplied from the other gas cylinder (the white space indicated by reference numeral G2). Arrow) flows from the top to the bottom of the figure. Hereafter, this gas is simply called shield gas.
A welding power is supplied by the main power source 6 between the electrode gripping portion 13 and the workpiece 2.

<Up and down movement of electrode part>
As described above, the tungsten electrode 1 a, the electrode support member 12, and the electrode gripping portion 13 are integrally configured to be able to move up and down in the torch by the compressed air from the air compressor 10. Although illustration is omitted, in this embodiment, a general air cylinder is applied as the vertical movement mechanism. Hereinafter, the tungsten electrode 1a, the electrode support member 12, and the electrode gripping portion 13 are collectively referred to as an electrode portion.
When air is supplied to the air supply port 1c, the electrode portion is pushed out and moves downward until the electrode gripping portion 13 contacts the inner wall of the nozzle 1b. When air is supplied to the air supply port 1d, the electrode part is drawn upward and returns to the original position. FIG. 4 shows a state in which the electrode portion is drawn upward.
<Configuration of electrode part>
5 and 6 are schematic views of the electrode portion.
FIG. 5 is a perspective view of the electrode portion viewed obliquely from below, and FIG. 6 is a front view of the electrode portion viewed from the direction of the white arrow in FIG. The electrode gripping portion 13 is provided with a plurality of protrusions 13a. When the electrode portion moves downward, the protrusion 13a comes into contact with the nozzle 1b and stops. In this embodiment, the height of each protrusion (projecting downward in FIG. 5) is about 0.5 mm, and the length (direction extending radially from the central axis of the electrode portion in FIG. 6) is about 1 mm. In FIG. 5 and FIG. 6, three such protrusions 13a are provided at intervals of 120 ° when viewed from the front, but the number and arrangement of the protrusions 13a are not limited to this.
However, if the contact area between the protrusion 13a and the nozzle 1b becomes too large, the amount of the oxide film attached due to the generation of a pilot arc, which will be described later, increases, so it is desirable to keep the contact area to the minimum necessary.

<Procedure from arc start to welding>
Subsequently, a procedure from arc start to welding in the non-consumable electrode type arc welding apparatus in the present embodiment will be described with reference to FIGS.
FIG. 7 is a timing chart showing the vertical movement of the electrode part from the arc start to the end of welding, the flow rate of the center gas and the shield gas, the current by the pilot power source, and the change of the current by the main power source. It is a sectional side view which shows typically the mode of the torch front-end | tip part in the same time.

<< Procedure 1: Approaching torch 1 to work 2 >>
First, the robot 3 is operated in accordance with a command from the controller 5, and the torch 1 is approached to the work 2 and moved to an appropriate position as shown in FIG. At this time, the electrode portion is pushed downward by the vertical movement mechanism.
When the torch is moved to an appropriate position, the controller 5 outputs a command to supply the center gas and the shield gas into the torch 1. The flow rate of the gas at this time depends on the shape of the gas path inside the torch, but the flow rate of the center gas G1 is about 5 to 20 L / min, and the flow rate of the shield gas G2 is about 5 to 10 L / min. Further, a voltage is applied by the pilot power supply 7 between the electrode gripping portion 13 and the nozzle 1b that are in contact with each other, and a current is conducted between the electrode gripping portion 13 and the nozzle 1b. The current value by the pilot power supply 7 is about 3 to 15 A although it depends on the shape of the nozzle. This state is indicated by t1 in FIG.
In FIG. 8, it seems that the path of the center gas G1 is blocked by the contact between the protrusion 13a of the electrode gripping portion 13 and the nozzle 1b, but the protrusion 13a has a shape as shown in FIGS. Even if the protrusion 13a is in contact with the nozzle 1b, a gap is formed between the electrode gripping portion 13 and the nozzle 1b. The center gas G1 flows out from the periphery of the tungsten electrode 1a through this gap.

<< Procedure 2: Generation of pilot arc by raising the electrode part upward >>
Subsequently, the controller 5 outputs a command to the air compressor 10 and pulls the electrode portion upward as shown in FIG. 9 by the vertical movement mechanism. This state is represented by t2 in FIG. The amount of movement of the electrode portion at this time depends on the structure in the torch, but is about 0.3 to 2.0 mm.
From the state in which current flows between the electrode gripping portion 13 and the nozzle 1b by the pilot power supply 7, the projection 13a and the nozzle 1b that are in contact with each other as the electrode portion moves upward are separated, but the projection 13a is When the short circuit with the nozzle 1b is released, the arc 14 as shown in FIG. 9 is generated from at least one of the plurality of protrusions 13a. Hereinafter, this arc 14 is referred to as a pilot arc. In the figure, the existence of a pilot arc is schematically illustrated for easy understanding.
As described above, a pilot arc is easily generated by suppressing the contact area with the nozzle 1b to the minimum necessary for the shape of the protrusion 13a. Further, the pilot power supply 7 superimposes a current of 10 to 20 A on the normal current value for 5 to 10 msec after detecting that the short circuit between the protrusion 13 a and the nozzle 1 b is opened. This ensures that a pilot arc is generated.
<Method for confirming pilot arc generation>
The pilot power supply 7 has a current and voltage feedback function, and it is easy to confirm the occurrence of the pilot arc in FIG. The generation of the pilot arc can be determined based on whether or not the current value and voltage value detected by the pilot power supply 7 satisfy a predetermined condition (for example, the voltage is 15 V or more when the current flows at 3 A or more).
<Advantages of Pilot Arc>
In this embodiment, only the pilot power source 7 which is a DC power source is used for generating the pilot arc. Since no high frequency power source is used, high frequency noise is not generated around and peripheral devices do not malfunction.
Further, the pilot arc is generated by the separation of the protrusion 13a of the electrode gripping portion 13 and the nozzle 1b, and the tip of the tungsten electrode 1a and the nozzle 1b are not brought into contact when generating the pilot arc, so that the electrode tip is consumed. Can be deterred.
Further, since a pilot arc is not generated between the tip of the tungsten electrode 1a and the nozzle 1b, an oxide film due to the pilot arc is not generated at the tip of the tungsten electrode 1a, and the tungsten electrode caused by the oxide film is generated. Deterioration of the start characteristic of the main arc between 1a and the workpiece 2 can be suppressed.

<< Procedure 3: Movement of pilot arc >>
When the electrode portion moves upward, the pilot arc 14 is pushed by the center gas G1 and moves to the tip portion of the tungsten electrode 1a as shown in FIG.
When the pilot arc 14 moves to the tip of the tungsten electrode 1a, the pilot arc 14 disappears and remains at this position. In this state, the pilot power supply 7 can maintain the pilot arc 14 by applying a sufficient voltage between the electrode portion and the nozzle 1b so that the arc is not interrupted by the center gas G1 (specifically, 30V or more).
In addition, by arranging the optical sensor 11 connected to the controller 5 toward the tip of the tungsten electrode 1a, the pilot arc 14 generated in the torch in FIG. 9 is changed to the tip of the tungsten electrode 1a as shown in FIG. It can be determined whether or not it has moved to the part. The arc light is very strong light, and even with a weak current of about 3 to 15 A, the amount of light is large. Therefore, the movement of the pilot arc 14 can be easily determined by the optical sensor 11.

<< Procedure 4: Generation of main arc >>
When the pilot arc 14 is located at the tip of the tungsten electrode 1a as shown in FIG. 10, the gas near the tip of the tungsten electrode 1a is ionized by the pilot arc 14. Further, since a voltage is applied between the tungsten electrode 1a and the work 2 by the main power supply 6, a main arc 15 is easily generated between the tungsten electrode 1a and the work 2 as shown in FIG. Flows. This state is indicated by t3 in FIG.
Thus, by maintaining the pilot arc 14 generated by the pilot power supply 7 at the tip of the tungsten electrode 1a prior to welding, the main arc 15 generated by the main power supply 6 can be smoothly generated in an extremely short time. Can be done.
Although the actual welding current value varies depending on the welding conditions, the main power source 6 can pass a current of about 10 to 500 A.

<< Procedure 5: Flow control of center gas G1 after generation of main arc >>
Until the main arc 15 is generated, the flow rate of the center gas G1 is set large in order to move the pilot arc 14 to the tip of the tungsten electrode 1a. However, the pilot arc 14 moves to the tip of the tungsten electrode 1a and moves to the main arc 15 After this occurs, the flow rate of the center gas G1 is suppressed to a value suitable for welding of about 0.2 to 2 L / min (t4 in FIG. 7). In FIG. 12, the thin black arrow indicating the center gas G1 represents the change in the flow rate.
Further, the pilot power source 7 is shut off (t5 in FIG. 7).
<< Procedure 6: Welding with main arc >>
Thereafter, welding to the workpiece 2 is performed by the main arc 15. This state is shown in FIG.

<< Procedure 7: After completion of welding >>
At the end of welding, first, the main power source 6 is shut off (t6 in FIG. 7), the center gas G1 and the shield gas G2 are stopped (t7 in FIG. 7), and then the electrode unit is moved by the vertical movement mechanism in preparation for the next welding. Press down (t8 in FIG. 7).
<Removal of oxide film>
When the electrode part is pushed down by the vertical movement mechanism, the projection 13a of the electrode gripping part 13 is pressed against the nozzle 1b with a large force, and the oxide film formed on both surfaces is scraped off by the pilot arc. Specifically, the force at the time of pressing is about 75N. By removing the oxide film by this pressing operation, the next pilot arc can be generated smoothly.
Since the protrusion 13a suppresses the contact area with the nozzle 1b to the minimum necessary, the amount of the oxide film attached is suppressed, and the oxide film can be sufficiently removed by one pressing operation.

<Pilot arc generation timing 1 and 2>
In the present embodiment, the torch 1 is approached to the work 2 in a state where the welding power is supplied in advance between the electrode gripping portion 13 and the work 2 by the main power source 6, and a pilot arc is generated after the approach is completed. A pilot arc is generated while 1 is approaching the workpiece 2 and is maintained at the tip of the tungsten electrode 1a. After the approach to the workpiece 2 is completed, the main power supply is used to connect the tungsten electrode 1a and the workpiece 2 between the two. A main arc may be generated.
According to this procedure, since the preparation for generating the main arc is completed during the movement of the torch, the time required for the entire welding operation and the time for which the main power source is activated can be shortened, and the work efficiency can be improved.
In the present embodiment, pure argon gas is used for both the center gas G1 and the shield gas G2, but helium, hydrogen, oxygen, etc. may be mixed with the argon gas depending on the requirement of welding quality.

In the first embodiment, the TIG welding apparatus has been described as an example. In this embodiment, the procedure from the arc start to the welding in the plasma welding apparatus will be described with reference to FIGS.
<Description of side cross section of plasma welding torch tip>
FIG. 13 shows a schematic diagram of a side cross-sectional view of the torch tip in plasma welding.
In FIG. 13, the same parts as those in FIG. The same applies to FIGS.
In the case of plasma welding, in order to narrow down the arc, the shape of the nozzle 1b 'surrounds the tip of the tungsten electrode 1a so that the tungsten electrode 1a is not exposed from the tip of the torch. The main arc generated from the tungsten electrode 1a is cooled and contracted when passing through the opening at the tip of the nozzle 1b ′, and is narrowed down.
Thus, in the case of plasma welding, the shape of the nozzle and the positional relationship between the tip of the tungsten electrode 1a and the nozzle are different from those in the case of TIG welding, but the electrode portion is the same as in the case of TIG welding, and the pilot power supply The pilot arc is generated between the projection 13a and the nozzle 1b ′ by 7 and then the pilot arc is moved to the tip of the tungsten electrode 1a so as to shift to the main arc by the main power source 6. Same as the case.

  FIG. 14 corresponds to FIG. 8 in the case of TIG welding, and shows a state in which the torch 1 is approached to the work 2 and moved to an appropriate position. In FIG. 14, it seems that the path of the center gas G1 is blocked by the contact between the protrusion 13a of the electrode gripping portion 13 and the nozzle 1b ′. However, as in the case of TIG welding, the protrusion 13a is shown in FIGS. Since the shape is as shown, there is a gap between the electrode gripping portion 13 and the nozzle 1b ′ even when the protrusion 13a is in contact with the nozzle 1b ′. The center gas G1 flows out from the periphery of the tungsten electrode 1a through this gap. A voltage is applied between the electrode gripping portion 13 and the nozzle 1b ′ by the pilot power source 7. This is the same as the state at t1 in FIG.

FIG. 15 corresponds to FIG. 9 in the case of TIG welding.
The electrode portion is drawn upward by the vertical movement mechanism, and the pilot arc 14 is generated from at least one of the plurality of projections 13a as in the case of TIG welding. This is the same as the state at t2 in FIG. In the figure, the existence of a pilot arc is schematically illustrated for easy understanding.
As described above, with respect to the shape of the protrusion 13a, the pilot arc is easily generated by suppressing the contact area with the nozzle 1b 'to the minimum necessary. Further, the pilot power supply 7 superimposes a current of 10 to 20 A on the normal current value for 5 to 10 msec after detecting that the short circuit between the protrusion 13 a and the nozzle 1 b ′ is opened. This ensures that a pilot arc is generated.
FIG. 16 corresponds to FIG. 10 in the case of TIG welding, and shows a state where the pilot arc 14 is moved to the tip of the tungsten electrode 1a by the center gas G1.
At this time, as in the case of TIG welding, the optical sensor 11 connected to the controller 5 is arranged toward the tip of the tungsten electrode 1a, so that the pilot arc 14 generated inside the torch in FIG. Thus, it can be determined whether or not it has moved to the tip of the tungsten electrode 1a. In the case of plasma welding, the pilot arc 14 is not exposed to the outside of the nozzle 1 b ′. However, since the arc light is very strong light, the movement of the pilot arc 14 can be determined by the optical sensor 11.
FIG. 17 corresponds to FIG. 11 in the case of TIG welding, and shows a state where the main arc 15 is generated. This is the same as the state at t3 in FIG.
Also in the case of plasma welding, the generation of the main arc 15 by the main power source 6 is extremely short by maintaining the pilot arc 14 generated by the pilot power source 7 at the tip of the tungsten electrode 1a prior to welding. The point that it can be performed smoothly in time is the same as in the case of TIG welding.
Also in this embodiment, as in the case of TIG welding, only the pilot power source 7 which is a DC power source is used for generating the pilot arc. Since no high frequency power source is used, high frequency noise is generated in the surrounding area and peripheral devices malfunction. There is no such thing as waking up. Further, since the pilot arc is generated by the separation of the electrode gripping portion 13 and the nozzle 1b, the tip of the tungsten electrode 1a and the nozzle 1b 'are not in contact with each other when generating the pilot arc, so that the consumption of the electrode tip is suppressed. Can do.
Further, since no pilot arc is generated between the tip of the tungsten electrode 1a and the nozzle 1b ', an oxide film due to the pilot arc is not generated at the tip of the tungsten electrode 1a. The point which can suppress the start characteristic deterioration of the main arc between 1a and the workpiece | work 2 is the same as that of the case of TIG welding.

Until the main arc 15 is generated, the flow rate of the center gas G1 is set large in order to move the pilot arc 14 to the tip of the tungsten electrode 1a. However, the pilot arc 14 moves to the tip of the tungsten electrode 1a and moves to the main arc 15 After this occurs, the flow rate of the center gas G1 is suppressed to a value suitable for welding of about 0.2 to 2 L / min (t4 in FIG. 7). In FIG. 18, the thin black arrow indicating the center gas G1 represents the change in the flow rate.
Further, the pilot power source 7 is shut off (t5 in FIG. 7).
Thereafter, welding to the workpiece 2 is performed by the main arc 15. This state is shown in FIG.

At the end of welding, as in the case of TIG welding, first, the main power supply 6 is shut off (t6 in FIG. 7), the center gas G1 and the shield gas G2 are stopped (t7 in FIG. 7), and then the upper and lower sides are prepared in preparation for the next welding. The electrode unit is pushed down by the moving mechanism (t8 in FIG. 7).
When the electrode part is pushed down by the vertical movement mechanism, the electrode gripping part 13 is pressed against the nozzle 1b ′ with a large force, and the oxide film formed on both surfaces is scraped off by the pilot arc. Specifically, the force at the time of pressing is about 75N. By removing the insulating film by this pressing operation, the next pilot arc can be generated smoothly.
Since the protrusion 13a suppresses the contact area with the nozzle 1b ′ to the minimum necessary, the amount of the oxide film attached is suppressed, and the oxide film can be sufficiently removed by one pressing operation.

  This application is based on a Japanese patent application (Japanese Patent Application No. 2009-253125) filed on Nov. 4, 2009, the contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1 Torch 1a Tungsten electrode 1b, 1b 'Nozzle 1c Electrode extrusion air supply port 1d Electrode pull-in air supply port 1e Cooling water discharge port 1f Shield gas (G2) supply port 1g Cooling water supply port 1h Center gas (G1) supply port 2 Work 3 Robot 4 Mounting jig 5 Controller 6 Main power supply 7 Pilot power supply 8, 9 Gas cylinder 10 Air compressor 11 Optical sensor 12 Electrode support member 13 Electrode holding part 13a Protrusion 14 Pilot arc 15 Main arc G1 Center gas G2 Shielding gas

Claims (9)

A torch comprising an electrode portion and a nozzle disposed on the outer periphery of the electrode portion with a gap therebetween;
Gas supply means for supplying a shield gas flowing through the gap between the electrode portion and the nozzle to the torch;
A first power source for generating a pilot arc by applying a voltage between the electrode portion and the nozzle;
A second power source for generating a main arc by applying a voltage between the electrode and the workpiece;
In the non-consumable electrode type arc welding apparatus provided with a control unit for controlling the first power source and the second power source,
The electrode part includes an electrode and an electrode gripping part for gripping a base part of the electrode,
The electrode gripping portion includes a protrusion protruding toward the nozzle on the nozzle side,
The non-consumable electrode type arc welding apparatus, wherein the torch includes a moving mechanism for moving the electrode portion in the long axis direction within the torch to contact and separate the protrusion and the nozzle.   The shield gas is circulated in the gap between the electrode gripping portion secured by the protrusion and the nozzle when the protrusion and the nozzle are brought into contact with each other by the moving mechanism. Non-consumable electrode arc welding equipment.   2. The pilot arc generated by the first power source is generated between the protrusion and the nozzle by bringing the protrusion and the nozzle into contact with each other and separating the protrusion from the moving mechanism. Non-consumable electrode arc welding equipment.   The said pilot arc is moved to the front-end | tip part of the said electrode by the said shielding gas, The said pilot arc is transferred to the main arc between the said electrode and a workpiece | work by the said 2nd power supply. Non-consumable electrode type arc welding equipment.   The non-consumable electrode type arc welding apparatus according to claim 1, wherein the moving mechanism is an air cylinder. The non-consumable electrode type arc welding apparatus according to claim 1, wherein the electrode gripping part and the nozzle are made of a copper alloy.   An articulated robot having the torch attached to the tip thereof and a robot control device that controls the robot, wherein the robot control device controls the first power source and the second power source as the control unit. The non-consumable electrode type arc welding apparatus according to claim 1.   The non-consumable electrode type arc welding apparatus according to claim 1, wherein the tip end portion of the electrode is exposed from the tip end portion of the nozzle to perform TIG arc welding.   The non-consumable electrode type arc welding apparatus according to claim 1, wherein the entire electrode is covered by the nozzle and plasma arc welding is performed.

Images